Abstract

The Al_2O_3 with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite (beta-Al(OH)_3) phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of 100°C per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from 100°C;to; 1100°C, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of Al(OH)_3toeta-Al_2O_3totheta-Al_2O_3toalpha-Al_2O_3 sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to gamma-Al_2O_3;at;350°C. It shows AlO(OH) gamma-Al_2O_3todelta-Al_2O_3toalpha-Al_2O_3 sequences. The gamma-Al_2O_3 compacted at 550°C shows a high surface area (138m2/g).

• Keywords: Spark plasma sintering (SPS);Hydrolysis;Bayerite;Bohemite;Compaction temperature;